Soaps & Detergents

The thing nobody tells first-time buyers

Most of what looks like dirt on a house, a fence or a shaded patio is not dirt. It is biological growth: algae, mildew, lichen. Pressure knocks the top off it and it comes back in weeks. A detergent kills it and it stays gone for a season or more. This is why a professional washing a house uses low pressure and a lot of chemical, and why a homeowner with a powerful machine and no soap gets a worse result and damages the siding doing it.

Once you accept that, the whole approach changes. You apply cleaner at low pressure through the black soap tip, you let it sit — the dwell time is where the work happens — and then you rinse at modest pressure. Pressure becomes the rinse step, not the cleaning step. That is also the only safe way to clean vinyl siding.

How the category divides

Oxygenated cleaners (sodium percarbonate based, often sold as “oxy”) are the default for homeowners. They work on organic growth, they are comparatively kind to planting, and they are hard to misuse. Slower than bleach, and they need to stay wet while they dwell.

Sodium hypochlorite mixes — household bleach, diluted — are what most professional house washing actually uses. Far faster and far more effective on heavy mildew, and far less forgiving: it kills plants, corrodes metal, bleaches fabric and needs genuine care. It also must never pass through your pump. The honest account is in bleach and pressure washers.

Surface-specific cleaners for concrete, wood, composite and vehicles. These exist because the surfaces have genuinely different needs: a wood cleaner has to rinse clean so a stain will take, and a car soap has to be pH neutral so it does not strip wax. A general-purpose bottle will clean all of them acceptably and none of them well.

Degreasers. A separate problem. No pressure and no general cleaner will lift motor oil out of a slab; that needs a product designed to draw it out, which is covered in the concrete cleaners picks.

Concentrate, ratios and why results vary so much

Almost everything here is sold as concentrate, which is good — you are not paying to ship water — but it means the result depends on your dilution. Too strong wastes money and risks the surface; too weak and people conclude the product does not work. Mix ratios, and how to work out how much mixed product a given area needs, are in house wash mix ratios.

How the soap gets out of the bottle and onto the wall is the other half. Some machines have an onboard tank. Most do not, and use a downstream injector, a venturi that draws from a bucket. Injectors only draw when a low-pressure soap tip is fitted — this single fact is behind the overwhelming majority of “my soap is not working” complaints. See how soap injectors work and, if yours already is not drawing, the fix page.

One bottle or four?

If this is your first season, buy one good all-purpose outdoor concentrate and use it on everything. You will learn which surfaces it struggles on, and that tells you which specialist bottle to buy second. Buying four bottles up front means three of them go solid in the garage. Do I need pressure washer soap covers the case where the answer is genuinely no.

Where to go next

Detergent only reaches the surface if your machine can apply it, so the two hubs that pair with this one are nozzles and hoses — specifically the black soap tip and the injector — and surfaces and how-to, which has the step-by-step method for each material, including when to apply and how long to let it sit.